Comparison of larval performance between Thai and Vietnamese freshwater giant prawn, Macrobrachium rosenbergii (de Man): a preliminary study

This study compared the performance of larvae of giant freshwater prawn (Macrobrachium rosenbergii) from Thailand and Vietnam. Thai broods were collected from a farm and Vietnamese broods were collected from a river. Larvae from these two sources were raised in identical environments, and their rates of development and survival as well as their ability to withstand environmental stresses were assessed. The first postlarval stage was observed in both strains on day 22. All larvae (100%) from Thai broods completed metamorphosis by day 36, but only 89% of the Vietnam strain completed metamorphosis by day 45. The stages of development were more uniform in larvae from the Thai stock than the Vietnamese stock. Survival differences were observed within the first week (92% in the Thai group vs. 55% in the Vietnamese group). These differences were most pronounced beginning in week 5 (52% and 16% respectively) and week 7 (33% and 2% respectively). No clear difference was found in brood size and fecundity between the two groups. No difference in survival was observed between the two groups of larvae challenged with salinity, oxygen or formalin. Differential development rates of larvae in the same batch would naturally create conditions favourable for cannibalism and impaired ability to capture food. The earlier and more uniform rate of development, and subsequent higher rate of survival of Thai stock compared with the Vietnamese wild stock is suggested to be due to inadvertent selection in the domesticated stock.     

樟子松引种驯化和遗传改良研究现状

樟子松为中国北方特有的珍贵树种,具有生长快、适应性、耐干旱瘠薄的优良特性,经济、社会和生态价值显著。因此,樟子松这一珍贵资源的引种驯化与遗传改良极为重要,在汲取国内外相关研究成果和学术观点的基础上,系统阐述了樟子松的种源试验、引种驯化、遗传改良、良种选育、种质保存及可持续利用等领域的研究现状和进展,指出了种质资源保存方面存在的不足,展望了种质资源可持续经营的广阔前景,提出了优异种质创新利用的具体思路和对策,以期为拯救并保护障子松资源提供理论参考。     

不同光照和水分处理对驯化栽培黄精株高的影响

以野生黄精鲜根为试材,研究驯化栽培中光照及水分对其株高的影响。结果表明:遮荫比全光照栽培利于株高生长,二者达极显著差异;灌溉措施仅在5月对株高影响显著,后期灌溉对株高影响不大。综合试验结果得出较优栽培措施:遮荫条件下,前期视垄表20 cm深墒情达20%以下及时灌溉,后期雨季无需灌溉,适当控水。     

欧洲白桦引种驯化及遗传效应评价

欧洲白桦（Betula pendula Roth．）为经济价值较高的工业用材和景观美化树种,生态适应性较强,分布广泛．为了丰富我国寒温带用材树种资源和生态城市建设种质资源的遗传多样性,遵循供种区与引种区环境条件相似原则,根据引种区土壤、植被分布、地形地貌和地理位置等主要环境条件,确定与之相适应的供种区．以欧洲白桦为研究对象,在引种驯化的基础上,系统开展家系子代的生长动态规律、变异性、生态适应性和抗逆性分析,综合评价遗传力和遗传增益等遗传参量的遗传效应．结果表明：欧洲白桦家系子代的生长趋势与东北白桦基本上趋于一致,能较快地适应新的生态环境,但生长性状存在一定的变异,其中：树高性状变异较小,地径性状变异较大,当年高生长变异最大,平均变异系数分别为2．50％,27．76％和50．31％．欧洲白桦的家系遗传力较强,遗传增益较高,遗传效应显著,3个性状的家系遗传力分别为0．7623,0．8083和0．6375,遗传增益分别为16．89％,17．97％及25．63％,应用前景广阔．     

石蛙养殖中几个关键时期的饲养管理技术

通过几年的实践，总结石蛙养殖中几个关键时期的驯养经验。在卵孵化期，特别要注意水质清新无污染，水中的溶氧量高。在蝌蚪生长期，必须关注饮食卫生，不要饲喂长时间煮过的饲料。在幼蛙生长期，对水质的要求十分严格，一定要按幼蛙身体大小饲喂不同大小的蚯蚓，特别是刚变态的幼蛙，最好饲喂小蝇蛆。     

文化意象的传递和翻译

文化意象的差异往往导致传递过程中的语义缺省和冲突.本文就文化意象的传递和翻译问题进行了探讨,强调译者应提高跨文化意识,结合异化和归化两种互惠互补的翻译策略,实现文化传真.     

Strong heritability across years and sites for pod wall proportion and specific weight in Lupinus albus and genotypic correlation with other pod and seed attributes

Thinner pod walls might contribute to increased yield potential and adaptation of lupins. Fourteen autumn‐sown genotypes of Lupinus albus L. were evaluated over 2 years at four sites in southern Chile. Pod wall proportion (PWP), pod wall specific weight (WSW) and five other pod‐related characters were measured to estimate their genetic variation, heritability across years and sites, and genotypic and phenotypic correlations among the characters. Ranges for PWP and pod WSW were 22.9−43.1% and 16.4−37.4 mg/cm², respectively. PWP in cultivated L. albus was similar to that reported in L. angustifolius; however, specific weight was substantially lower. Highly significant genotypic effects were found for both characters. Broad sense heritabilities were high for PWP (0.63) and moderate for pod WSW (0.46). These characters were significantly correlated, more so genotypically (r_g = 0.67) than phenotypically (r_ph = 0.36). Selection for low PWP should lead to lower pod wall thickness or density, both of which contribute to pod WSW. Nevertheless, selection for pod WSW could achieve further reductions, particularly if practised among low PWP materials.     

The domestication and improvement of cowpeas (Vigna unguiculata (L.) Walp.)

Summary Physiological and morphological characteristics of the two wild and three domesticated subspecies of cowpeas are compared. The wild accessions are alike in having small, hard seeds borne in dehiscent pods, but differ in other characteristics. We suggest that the wild subsp. dekindtiana, from the seasonally-arid tropics, is more likely to have been the progenitor of modern cowpeas than the other wild subspecies (subsp. mensensis), but that subsp. dekindtiana was first cultivated in the humid tropics where its pods are slow to dehisce. Domestication has been associated with changes in the structure of pod valves and seed coats which reduce pod dehiscence and seed hardness. Pods and seeds have increased in size, mainly by increases in the rate of dry weight accumulation, and their increase has been only partly paralleled by increase in the area of subtending leaves. There has been no increase in the maximum photosynthetic rate of leaves, but the duration of their photosynthetic activity has increased. Domesticates are less sensitive than are wild plants to some environmental controls, such as in the response of germination to temperature, but in their flowering responses to daylength both wild and cultivated forms retain sensitivity under conditions where this is of adaptive value.     

Occurrence and chromosome number of Cucumis sativus var. hardwickii (Royle) Alef. in South India and its bearing on the origin of cultivated cucumber

Summary Cucumis sativus var. hardwickii (Royle) Alef., the wild progenitor of cultivated C. sativus is reported for the first time from peninsular India. The South Indian specimens showed n=7 bivalents in PMCs. The discontinous occurrence of the wild taxon in the Himalayan regions and peninsular hills and the existence of cultivars of C. sativus adapted to the tropical and temperate climates suggest polytopic domestication of the cultivated forms. The possibility of utilizing this wild germplasm for crop improvement is indicated.     

The occurrence and inheritance of a brittle rachis phenotype in Italian durum wheat cultivars

Italian and Tunisian durum wheats from different eras of breeding were assessed for the presence of a gene for brittle rachis. Nine of 15 Italian durum landraces had brittle rachides. Strampellis achievement was the release of the well-known variety, Senatore Cappelli, which was derived from a Tunisian landrace, Jenah Rhettifah, which has a brittle rachis. Rachides of two Tunisian landraces were also brittle. Since the 1950s, 16 accessions were released as selections from crosses or mutagenesis involving Senatore Cappelli. Seven of these accessions have brittle rachides. F₂ segregation in intercrosses of Senatore Cappelli with other durum accessions with brittle rachides indicated a common allele for brittle rachis. Segregation of the F₂ from Senatore Cappelli/ANW 10A and the F₂ of Senatore Cappelli/ANW 10B showed that the gene for brittle rachis of Senatore Cappelli was allelic to the brittle allele of the Br-B1 locus on chromosome 3B. Senatore Cappelli was presumably the only source of brittle rachis used in Italian breeding programmes. The genes for brittle rachis have been retained in the gene pool of durum wheat, suggesting that the brittle rachis character is not associated with an appreciable yield loss in modern farming systems in Mediterranean environments.